1. Field of the Invention
The invention relates to a drum rotor for an axial-flow turbomachine, in which the blades are fastened with their roots in rows in encircling blade grooves having lateral supporting prongs.
2. Discussion of Background
EP 0 520 260 B1 discloses drum rotors of this type. As a result of the rotor deflection, the encircling blade grooves change their axial dimension during every rotor revolution. Due to the alternating stresses arising in the process, damage can occur at the rotor recesses. In addition, pronounced asymmetrical displacements can occur in the first blade groove during temperature changes, for example during operational fluctuations. In order to avoid damage, an encircling preliminary groove which is not fitted with blades is normally arranged in front of the first blade groove. However, this preliminary groove weakens the drum rotor and disturbs the flow of the working medium. The preliminary groove is therefore usually fitted with closure segments. The preliminary groove and the closure segments result in additional expenditure of labour during production and assembly as well as additional material consumption.